This application relates to a mold board assembly in which the mold board is resonantly driven to both cut and agitate the material to be moved. In this context the term "mold board" includes both the type of mold board used in a bulldozer and a shovel used in a front end loader.
Applicant's U.S. Pat. No. 4,359,102 shows bulldozer having a reciprocating cutter blade at the base of the mold board. A resonant beam drives the cutter blade intermittently forwardly to cut the material to be dozed. This bulldozer construction has been found to be quite useful because it loosens the earth to be moved by the bulldozer, substantially reducing the force that must be applied to dislodge the earth and the size of the tractor needed to advance the mold board. However, this construction still is not as efficient as desired, because the earth and other material, once dislodged by the cutter, remains compacted together and is difficult to move.
Various prior devices have attempted to break up the earth and make it easier to move. U.S. Pat. No. 3,443,327 shows a front end loader with a shaker for vibrating the entire shovel. U.S. Pat. No. 3,770,322, particularly FIGS. 25 and 26, shows a mold board which is shaken by an oscillator. U.S. Pat. No. 3,367,716, particularly FIG. 22, shows a similar arrangement. Unfortunately, these devices provide immense stresses on the mold board, and vibrate the overall system, making them impractical. Also, such devices in effect combine the cutting and agitation functions, and have been found not to be as effective as desired for either task.